745 
fxus63 keax 201728 
afdeax 


Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO 
1128 am CST Thursday Nov 20 2008 


..updated aviation discussion... 


Discussion... 


Forecast area will be under strong cold air advection today as a 
strong 1050 high centered in central Canada...plunges south into the 
central U.S. By 12z Friday. A thin layer of moisture accompanying 
this surge of colder air has produced a stratus deck over the upper 
Midwest that has spread into the forecast area overnight. Models 
having trouble capturing this moisture since it is so thin...but 
judging from the NAM condensation pressure deficits...the initial 
band of clouds currently in the region should continue to drop south 
out of the area this morning as some moisture around the 700 mb level 
moves over top...so may not see much sunshine this morning. This 
afternoon though...may see some SC form but should be enough holes 
to allow the sunshine to warm the airmass a bit despite the strong 
cold air advection. Still...will lean toward the colder met guidance given 
temperature profiles upstream this morning. Also...will remove 
mention of flurries we had going in northeast portion of the 
forecast area with the thin low level moisture. 


For tonight...with the surface high axis sliding into eastern Kansas 
and northwest Missouri...and some very dry air moving into the 
region...should see a good radiational cooling set up. Given still 
some warmth in the ground and effects of the city...hesitate to go 
as cold as the met numbers for the kc metropolitan area...but will trend 
toward them for rest of area...especially for the more low lying 
spots. 


Have not made any significant changes to the rest of the forecast. 
The one thing to watch will be a fast moving short wave trough 
currently of the Pacific northwest coast...which will move into the 
Dakotas by Friday evening...and into Iowa by 12z Saturday. This 
system will be pretty moisture starved as there will be no time for 
any return flow to bring moisture back into the forecast area before 
its arrival. The European model (ecmwf) hints that some light precipitation may occur 
in northern Missouri by 12z Saturday as a jet maximum and diffluent 
upper flow affects the region...but given the lack of low level 
moisture...will opt for the dry forecast at this point. 


For Sunday...with the surface ridge east of the region...a return 
flow may be able to bring enough low level moisture back to the 
region to support rain showers as yet another short wave trough 
develops over the north central part of the country. Will leave the 
slight chance probability of precipitation that the previous forecast had going across the 
southeast half of the forecast area...although onset of these 
showers may be delayed until Sunday evening as the better moisture 
may not arrive until then. Another surge of colder air will arrive 
the first of the week in the wake of Sunday short wave. 


Pc 


&& 


Aviation... 


Middle cloud deck was beginning to shift south of the Kansas City 
terminals at noontime...which will allow for a brief window of 
sunshine and increasing surface winds due to mixing. Frequent 
northerly gusts of 25 to 28 knots...possibly an isolated 30 knotter 
will buffet the terminals this afternoon. 


Any sunshine that does occur will allow the boundary layer to 
destabilize...resulting in the development of widespread 
strato-cumulus this afternoon. Any ceilings should be 
VFR...averaging around 3500 feet above ground level...but will forecast a 
predominantly broken ceiling through much of the afternoon. 


Winds will gradually diminish at sunset...but remain out of the 
north at 8 to 12 knots through midnight. A light and variable wind 
will then develop for the remainder of the overnight hours into 
early Friday under clear skies. 


Bookbinder 


&& 


Eax watches/warnings/advisories... 
MO...none. 
Kansas...none. 


$$